The performance of insulating paper cellulose is an important factor affecting the normal operation of electric power equipment. This paper uses molecular dynamics methods to establish pure cellulose, hBN‐modified cellulose, 3‐aminopropyltriethoxysilane (KH550), 3‐glyoxypropyltrimethoxysilane (KH560), and 3‐methylpropoxypropyltris (KH570) grafted with hBN modified cellulose models. The effect of cohesive energy density (CED), thermal conductivity (TC), mean square displacement (MSD), free volume, glass transition temperature (Tg), and mechanical properties on the thermomechanical properties of cellulose are investigated and compared. The results indicate that all three silane coupling agents can enhance TC, thermal stability, and mechanical properties of the cellulose models. Among them, KH550 is the best grafting method for hBN/cellulose system as KH550 graft not only significantly enhances TC by 114.29% and Tg by 23.88% but also significantly strengthens the toughness and resistance to deformation of cellulose by over 50%.

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Ladderlike polyphenylsesquioxane (L‐PPSQ) with special planar ladder structure is significant to upgrade the mechanical strength of cellulose insulation paper. In this study, the effect of different content of L‐PPSQ on mechanical properties and dielectric properties of cellulose is first investigated by molecular simulation, and then insulation paper doped with L‐PPSQ is prepared for experimental verification. It is indicated in the simulation results that the elastic modulus, bulk modulus, and shear modulus of the cellulose are enhanced up to 36.82%, 27.96%, and 41.80%, respectively, when L‐PPSQ is added at 3 wt%, and the cellulose model with 3 wt% L‐PPSQ possesses the lowest dielectric constant. The reason is that L‐PPSQ can enhance the hydrogen bonding network of cellulose, weaken the degree of molecular chain motion, and strengthen the strength of molecular chains, which in turn manifests as the enhancement of mechanical strength. It is shown in the experimental results that the tensile strength and elongation at break of the composite insulation paper can be enhanced by 16.7% and 35.09% when the L‐PPSQ content is 3 wt%, which is consistent with the simulation results. The short‐term aging test shows that L‐PPSQ can also upgrade the mechanical strength of the insulation paper at high temperatures.